This invention relates to a process for chemically modifying textile articles which contain hydrolizable polymers to reduce pilling tendency.
Hydrolizable polymers, such as polyester, possess many attributes that lead to their use for many items of commerce, such as fibers, films and molded products. Among these attributes are strength and toughness of the products, lack of reactive surface groups that can lead to staining, and various other advantages. However, many of these attributes can become problematic for certain end uses of the polymers. For example, the tenacity and other strength properties of the hydrolizable polymers such as polyester contribute to their outstanding performance as textile fibers and various other applications, such as films. However, this same strength characteristic can result in a phenomenon known as pilling if this fiber is manufactured, for example, into a spun yarn or in the manufacture of certain microdenier yarns.
Pilling results from fibers being pulled out of the fiber bundle and becoming entangled into a xe2x80x9cballxe2x80x9d due to mechanical action, such as rubbing that, for example, fabrics encounter during normal use. Fabrics composed of cellulosic fibers experience similar action, but because the fiber is much weaker, the xe2x80x9cpill ballsxe2x80x9d tend to break off before they become objectionable. These xe2x80x9cpill ballsxe2x80x9d are a detriment to the appearance and comfort of textile articles. Reducing or eliminating the pilling propensity of hydrolizable polymer-containing textile articles would typically extend the useful life of the end-use product, such as a garment, by retaining its original appearance and comfort. Various products introduced by the fiber producers, such as low pill T-351 Trevira(copyright) polyester fiber from Hoechst-Celanese, have resulted in some degree of success in reducing pilling tendency. U.S. Pat. No. 3,104,450 to E. I. du Pont de Nemours and Company suggests that by controlling the relative viscosity and the break elongation of polyester fibers, one can reduce the pilling tendency of fabrics containing those spun polyester yarns.
Two major disadvantages are typically associated with fiber modifications made by the fiber producers in attempting to resolve the pilling issue. First, if the fiber producer lowers the fiber strength to the level required for good resistance to pilling, it becomes difficult for the yarn manufacturer to spin the yarn without excessive breaks and resulting off-quality. This necessitates further treatment to adequately reduce the yarn strength, such as alkaline hydrolysis after fabric formation or in a subsequent laundering step, to provide good resistance to pilling. Second, due to the vast number of fiber options (such as denier, cross-section, staple length, etc.) desired in the market, the fiber producer experiences cost, quality, and capacity issues associated with the spinning of small quantities of specialty fibers.
Textile manufacturers face a multitude of challenges in attempting to resolve the pilling issue on textile articles containing hydrolizable polymers. For example, textile chemists have applied binders to increase the force required to remove fibers from the fiber bundle; however, this typically results in detrimental changes to the feel of a fabric, and the effect is generally reduced by washing the fabric or end-use product (i.e. a garment). Some effort has been devoted to lowering the fiber strength by various chemical treatments. Hydrolysis with, for instance, sodium hydroxide does indeed lower the fiber strength, but it is difficult to precisely control this process and the resulting fabric also undergoes a significant weight loss. Aminolysis of the ester linkage of the polymer, such as addressed by Farmer in commonly-assigned U.S. Pat. No. 4,103,051, incorporated by reference herein, indeed can achieve the desired properties in many instances, but also can adversely affect the dyeing of the resulting fabric. This disadvantage is addressed by commonly-assigned U.S. Pat. No. 6,113,656 to Kimbrell which discloses a method for improving the dyeing of fabric treated with the Farmer chemistry. In addition, the structure of the amines disclosed by Farmer, especially those preferred by Farmer, can lead to chemical handling issues in textile finishing facilities (as will be discussed further herein) and also to quality issues resulting from attempting to handle such chemicals. Furthermore, it has proven difficult to control the batch to batch variation, within a somewhat narrow range, on certain styles, which in turn, leads to significant treated yardage that is not acceptable, either due to poor pilling performance or excessive strength loss.
More specifically, Farmer describes in U.S. Pat. No. 4,103,051 that organic amines are a particularly preferred class of compounds for this type of reaction, resulting in generally good control of the degree of pilling improvement obtained. Farmer discloses the use of aliphatic amines containing at least 10 carbon atoms. In addition, Farmer states that fatty diamines such as n-coco-1,3-propanediamine, are the preferred amines for this process.
It has been found that the use of the above-mentioned fatty diamines can impart detrimental variability to the textiles treated by this process. First these fatty diamines, especially those containing greater than 10 carbon atoms, tend to solidify at or around room temperature. This necessitates special storage and handling requirements in a typical textile dyeing operation such as, for example, drum heaters or other heating equipment to maintain the amine at a temperature above its melting point. Second, these compounds, such as the n-coco-1,3-propanediamine preferred by Farmer, are mixtures of unbranched carbon chains containing from 8 to 18 carbon atoms. This mixture tends to separate according to the size of the carbon chain resulting in unacceptable variations of the chemical composition and the degree of strength reduction obtained by this process. This again leads to special chemical handling requirements to minimize this potential variable, such as the use of drum mixers. Finally such diamines are known to adsorb and react with carbon dioxide from the air, resulting in an insoluble carbamate that does not react with polyester or other hydrolizable polymers. Without special attention to controlling the exposure of these amines to the air, various mixtures of products result. The net result can be less than the necessary amount of active amine being used to obtain the required strength reduction necessary to achieve good pilling performance. All of these potential chemical variations result in a process that can be very difficult to control within acceptable product performance tolerances.
In light of the foregoing discussion, it is one object of the current invention to achieve a textile article, which contains hydrolizable polymers that have been chemically modified by branched chain amine treatment, that has consistently good pilling and acceptable strength characteristics. A textile article includes fiber, yarn, fabric, film, etc. or any combination thereof. The textile article may be dyed or undyed. As used herein, a hydrolizable polymer is or includes any polymer that is capable of undergoing a hydrolysis reaction, such as, for instance, polyester. The term hydrolysis is used herein to include any reaction that typically results in the cleavage of the ester linkage in the polymer. Without being bound by theory, it is believed that this cleavage is the mechanism by which the textile article is weakened and improved resistance to pilling is obtained. Hydrolysis can include the addition of water, resulting in the re-formation of carboxylic acid and alcohol moieties, and can include a reaction with acids or bases. If amines are utilized, the resulting decomposition products are an alcohol and an amide. Hydrolysis reactions can also occur with polymers such as wool, such that an amide linkage is cleaved. However, this reaction typically requires more robust treatment conditions such as increased temperature, increased amine concentration, etc.
By good pilling, it is meant that the article achieves a minimum 3.0 rating after 30, 60, or 90 minutes when tested for Random Tumble Pilling according to ASTM test method D 3512-99A and is typically dependent upon the composition of the article being treated, the method of manufacture of the article, the amine used for treatment, etc. The amount of strength that will generally be considered to be xe2x80x9cacceptablexe2x80x9d is the strength required for the treated article to function within its anticipated end product for a minimum number of use or wear cycles, which will generally also include intermittent cleaning cycles as well. The strength that is considered to be acceptable for a given article will therefore vary depending on the type of treated article, how it will be used in an end product, the type of end product, etc. By way of example, acceptable strength for an article intended for use in knit shirting is achieved with a minimum 50 pound rating when tested for Mullen Burst Strength according to ASTM test method D 3786-87. More specifically, by experience it has been determined that a certain double knit (24 gauge) 100% polyester tuck fabric to be used in knit shirting should have strength of about 50 pounds, but no more than 90 pounds, when tested for Mullen Burst Strength according to ASTM test method D 3786-87, and preferably, between 55-65 pounds. If the Mullen Burst Strength exceeds 65 pounds, unacceptable pilling performance is obtained on this particular style. If the Mullen Burst Strength drops below 50 pounds, the fabric is generally considered to be too weak for apparel applications and holes may be punctured into the garment during normal use conditions.
As an ASTM test method, Mullen Burst Strength is typically used for determining the strength of knit or non-woven fabrics. If the treated fabric is a woven fabric, or if fibers or yarns are modified by the process of the current invention, other methods for determining the strength of the textile article must generally be used. By way of example, these methods include determining the tear strength of a woven fabric or determining the tensile strength of the fibers or yarns using test methods which are known and available to those skilled in the art.
Similarly, other standard methods for evaluating the pilling resistance of fabrics or fibers and yarns exist and may be used. By way of example, these methods include Brush and Sponge, Martindale and Elastomeric Pad methods which are known and available to those skilled in the art.
A second object of the current invention is to achieve a textile article, which contains hydrolizable polymers that have been chemically modified by branched chain amine treatment, that maintains its aesthetic appearance and comfort properties due to its improved resistance to pilling. The formation of xe2x80x9cpill ballsxe2x80x9d leads to an unsightly appearance of the article. In addition, these xe2x80x9cpill balls,xe2x80x9d when found in a garment, for example, generally result in a loss of garment comfort due to the abrasive nature of these protrusions against the skin. Therefore, reducing or eliminating the formation of xe2x80x9cpill ballsxe2x80x9d allows for the extension of the useful life of textile articles, such as apparel, made from hydrolizable polymer-containing fabric.
It is also an object of the current invention to achieve a method for modifying textile articles, such as fabrics containing hydrolizable polymer fibers and/or yarns, with branched chain amines to reduce their propensity to pill while at the same time maintaining acceptable strength characteristics. The chemical structure of these amines improves both the process of modifying the hydrolizable polymer-containing textile articles and reduces or eliminates certain quality and cost issues associated with variations in this process. These variations are believed to be caused by the chemical compositions of amines disclosed in the prior art and the chemical handling procedures typical in a textile dyeing and finishing operation. This method also generally reduces the process and product variability associated with the prior art.
It is another object of the current invention to achieve a substituted hydrolizable polymer wherein the substitute is a branched chain amine. It is generally believed that this polymer is a reaction product that is formed after the textile article has been treated with the branched chain amine.
Other objects, advantages, and features of the current invention will occur to those skilled in the art. Thus, while the invention will be described and disclosed in connection with certain preferred embodiments and procedures, such embodiments and procedures are not intended to limit the scope of the current invention. Rather, it is intended that all such alternative embodiments, procedures, and modifications are included within the scope and spirit of the disclosed invention and limited only by the appended claims and their equivalents.